1. Field of the Invention
The present disclosure relates to an electro-magnetic contactor having a function of sensing the status of input power that supplies electric energy to a power input end of the electro-magnetic contactor and an electro-magnetic contactor monitoring system for monitoring the same from a remote location.
2. Background of the Invention
An electro-magnetic contactor is one of devices for supplying or cutting off power to a load among equipments of elements constituting a factory automation system. The electro-magnetic contactor is a device for controlling a motor through the opening or closing of power. As a device using the principle of an electromagnet, the electro-magnetic contactor implements supplying or cutting off main power to a load circuit when control power is applied or cut off to the contactor, namely, according to a switching signal. In other words, the electro-magnetic contactor supplies or cuts off power to a load according to whether the electromagnetic coil which is one of elements constituting the breaker is excited or not.
FIG. 12 is a block diagram illustrating the configuration of a typical electro-magnetic contactor. Here, reference numeral 10 is input power. The input power 10 may be direct current or alternating current power. A surge absorption unit 21 absorbs and removes a surge voltage contained in the input power 10. A noise filter circuit unit 22 removes a noise component contained in the power from which the surge voltage is removed in the surge absorption unit 21. A rectifier circuit unit 23 rectifies power outputted from the noise filter circuit unit 22 and converts it into direct current power. Reference numeral 25 is an electromagnetic coil, and the electro-magnetic contactor may include only an electromagnetic coil as the need arises. Reference numeral 24 is a discharge circuit unit. The electromagnetic coil 25 and discharge circuit unit 24 are connected in parallel to each other, and the parallel connected one side terminal is connected to an output terminal of the rectifier circuit unit 23. A pulse width modulation unit 27 generates a pulse signal having a predetermined width as a switching signal. For a switching unit 26, an output terminal of the pulse width modulation unit 27 is connected to a gate of the transistor (FET1) and a ground terminal (R1) is connected thereto to detect a current flowing through the electromagnetic coil 25, and a drain of the transistor (FET1) is connected to the other side terminal of the parallel connected electromagnetic coil 25 and the discharge circuit unit 24. In the electro-magnetic contactor having the foregoing configuration, when power is supplied through the input power 10, the surge absorption unit 21 absorbs a surge voltage from the input voltage, and the noise filter circuit unit 22 filters out noise, and the rectifier circuit unit 23 rectifies the filtered voltage and outputs a direct current voltage. Here, when the voltage input to the input power 10 is a direct current voltage, the electro-magnetic contactor may not include the rectifier circuit unit 23. When power is supplied in such a state, the pulse width modulation unit 27 generates a pulse signal having a predetermined width, and the generated pulse signal is applied to a gate of the transistor (FET1) of the switching unit 26. Then, the transistor (FET1) repeats a conducting state and a cut-off state according to the pulse signal outputted from the pulse width modulation unit 27. When the transistor (FET1) is in a conducting state, the output power of the rectifier circuit unit 23 flows to the ground through the electromagnetic coil 25 and transistor (FET1). Then, when the transistor (FET1) is in a cut-off state, power that has been stored in the electromagnetic coil 25 when the transistor (FET1) is in a conducting state flows through the discharge circuit unit 24. Accordingly, the electromagnetic coil 25 continues to maintain an excited state, and due to this, the electro-magnetic contactor continues to maintain a closed state to supply power to the load.
In order to operate the electro-magnetic contactor, an inrush current should be applied to the electromagnetic coil at an initial stage to move the moving core. If the moving core is adhered to the fixed core, then the operating state is maintained even when a holding current far less than the inrush current is applied the electromagnetic coil.
However, if a capacity shortage phenomenon of the operating power in the electro-magnetic contactor, a voltage variation due to the starting load, a lightning, and the like are generated at the time point when an inrush current is applied to the electromagnet of the electro-magnetic contactor, then an instantaneous voltage sag or transient voltage surge may be generated. Due to such a phenomenon, the voltage of the operating power in the electro-magnetic contactor may be less than the operating voltage of the electro-magnetic contactor, and the inrush current continues to flow through the electromagnetic coil, and thus the insulation layer of the electromagnetic coil may be damaged to cause a burn or chattering, thereby creating a problem that the load is damaged by a fire. If a transient voltage is continuously induced, then the insulation layer may be damaged due to an increase of the current flowing through the electromagnetic coil, thereby causing a tremendous loss to the factory automation system.